1. Field of the Invention
The invention relates to a pump impeller for a hydrodynamic torque converter with a flange and a hub located radially inside and extending in the axial direction. A seat for a bearing is formed on the hub.
2. Discussion of the Prior Art
A pump impeller of this type is known, for example, from German reference DE 43 44 562 C1. In this reference the pump impeller is driven by the crank shaft of an internal combustion engine, which crank shaft is connected to the hub.
The pump impeller is usually designed as a drawn sheet-metal part. Because the seat of the bearing is on the hub, the hub must be precisely worked radially inside or radially outside. In addition, higher strength requirements are placed on the hub than on the outer shell of the pump impeller. To economically fulfill these two demands, the hub in the known pump impeller is made of a different material than the outer shell and is connected by a friction weld connection to a flange mounted radially inside the outer shell.
Pump impellers are also known in which the hub is welded directly to the outer shell or is embodied in one piece therewith.
A weld connection has the disadvantage that the hub and the flange or outer shell must be previously centered relative to each other. In addition, the welded connection must be produced with care to avoid later failures of the torque converter due to cracks or the like in the weld seam. Because the hub can warp during welding, the bearing seat cannot be produced until after the two parts are connected. Handling the pump impeller is then complicated, because of its shape.